What Is PT-141?

PT-141 is a peptide, a short chain of amino acids made in a laboratory. Its official name is bremelanotide. It resembles part of alpha-melanocyte-stimulating hormone, or alpha-MSH, a natural messenger the body uses for several jobs at once.

A Small Ring

Most peptides are straight chains. PT-141 is different: its seven amino acids are linked so that six of them form a closed ring. This shape protects it from being broken down as quickly as the natural hormone. Chemically it is almost identical to the earlier tanning peptide it came from, which explains why the two are often confused.

What Happens in the Body

• The switches: PT-141 attaches to melanocortin receptors, a family of receptors found in the brain and in other tissues.
• The main target: its key action is on the MC4 receptor, which sits in brain areas involved in motivation and sexual response.
• The outcome: in animal studies it increased interest in a partner rather than simply triggering a physical reflex.
• The side effects: the same receptor family also affects the gut, blood pressure and skin colour, which explains nausea, flushing and, in a few people, darker patches of skin.

How It Differs From Erection Pills

Pills such as sildenafil relax the blood vessels of the penis and only help once arousal has started. PT-141 acts earlier, in the brain. In early trials it caused erections in healthy men even without any sexual images, something blood-flow pills do not do.

This brain-based action is also why it was tried in women. Low sexual desire is a common complaint, and medicines that work on blood flow had not been a real answer to it.

In Short

• PT-141 is a seven-amino-acid ring peptide, also known as bremelanotide.
• It acts on melanocortin receptors in the brain, not on blood vessels.
• Nausea is its best-known side effect.
• It is approved only in the US and only for one condition in women.